Vulcanization of rubber



Patented July 25, 1939 UNITED STATES PATENT ()FFICE mesne assignments,to Company, New York,

New Jersey United" States Rubber N. Y., a corporation of No Drawing.Original application- March; 5,

1935, Serial No. cation June 28,

8 Claims.

This invention relates to new accelerators of the vulcanization-ofrubber and similar vulcanizable materials, and more particularly tomanners of using the same.

This case is a division of case Serial No. 9,385, filed March 5, 1935.

Broadly the invention comprises incorporating in rubber prior to actualvulcanization, an arylene thiazyl sulphide derivative of a productresulting from reacting hexamethylenetetramine with a mineral acid saltof a saturated or unsaturated hydrocarbon residue of the open chainseries.

More specifically the invention relates to the accelerators produced byreacting hexamethylenetetramine with a halide of an aliphatichydrocarbon, e. g., an alkyl, alk-ylene or alkylidene group, and thentreating the resulting reaction product with a mercapto-aryl thiazole,preferably in the form of a salt thereof such as an alkali salt of amercapto-aryl-thiazole,

Example 1.Preparation of hexamethylenetetramine-ethyl chloride reactionproduct:

450-parts of hexamethylenetetramine are placed in an autoclave havingsteam and water connections for heating and cooling purposes, and thehexa-methylenetetramineheated-to about C. 202 parts of ethyl chlorideare gradually added thereto. The rise in pressure is controlled bycooling Water circulation. The internal pressure rises to" aboutZOO-pounds per sq. inch and falls off to about 100 pounds in an hour.Steam at 90-pounds per sq. inch pressure is then introduced into theautoclave heating coils and the mix is heated so as to bring theinternal pressure" up to about -225 lbs. per sq. inch. The autoclave isthen cooled. The reaction product may be treated in the impure form witha thiazole salt or it may be further purified before reacting withthemercapto-aryl-thiazole. If the reaction product is treated with, forexample, 455 parts of caustic soda (50% solution) the free base isliberated. The free base is an oil and analyzes about 16.9% nitrogen.

A likely explanation of the reaction with hexamethylenetetramine is thatthe aliphatic halide addsto the hexamethylenetetramine, which additionproduct under reacting conditions breaks down to form formaldehyde andan acid salt or addition product of an aliphatic amine, e. g.,ethylamine hydrochloride, which materials react to form the acidaddition product, e. g the hydrochloride of the free base. This view issupported by-the fact that the product of reaction of ethylaminehydrochloride (1 mole) and. formaldehyde (1- mole) has propertiesapparently like 1935, Serial No. 28,809

Divided" and thisapplithose of the said acid free base.

Hence it is. to beunderstood that it is within the scope of the presentinvention to usethe mercapto-aryl thiazole derivatives of the acidaddition products produced by-reacting equi-molecular proportions offormaldehyde and an aliphatic amine hydrochloride such as thehydrochloride of ethylamine or other mineral acid salt of the amine suchas the sulfate, hydrobromide, phosphate, etc. oxidizing acids such asnitric are excluded. Instead of using a primary aliphatic amine such asethylamine there may be used the amines of other hydrocarbons disclosedherein.

The amine salt (50% solution in water) may be refluxed with Formalin forabout four hours, the resulting acid addition product cooled and treatedwith sodium mercapto benzo thiazole solution, or the acid additionproduct may be neutralized with alkali and the free base reacted withmercapto-benzothiazole.

Instead of ethyl chloride there may be used for reaction withhexamethylenetetramine, ethyl iodide or bromide, methyl chloride, iodideor bromide, isopropyl chloride, bromide or iodide, tertiary butylchloride, iodide or bromide, tertiary amyl chloride, iodide or bromide,ethylene chloride, ethylene bromide or iodide, ethylidene chloride,bromide or iodide, alpha chlor ethyl benzene, etc. or mixtures of any ofthese salts.

The aliphatic halide maybe reacted with hexamethylene-tetramine per seor its aqueous solution. The temperatures of reaction may range fromabout 100 C. to about C., and the amounts of halide permole ofhexamethylenetetramine may vary from 1 to 4 moles. Reflux conditionswithout pressure may be used, but the results are-not as good as Wherepressure or autoclavic treatment is resorted to.

The production and use of the accelerator is illustratedbelow.

Example 2.10 parts of the free base (16.9% N) of Example 1,.is taken upin 40 parts of hydrochloric acid (sp. gr. 1.19) and 50 parts of water,and mixedv With a solution of 7 parts of mercaptobenzothiazole dissolvedin 32 parts of caustic soda (50% solution) and 50 parts of water.Instead of sodium hydroxide, other alkali may be used to dissolve themercaptobenzothiazole and form an alkali salt thereof. On mixing, areaction takes place with evolution of heat and separation of a viscousbrown resin which may be washed with Water to further purify it.

addition product of the Example 3.A cold solution of about 16.7 parts ofmercaptobenzothiazole, 10 parts of sodium hydroxide (50% solution) and50 parts of water are added to 30 parts of the hydrochloride of the freebase (16.5% chlorine) of Example 1, with cooling.

' An oil separates out at the bottom and may be etc. as well assubstitution products washed with water to further purify it, ifdesired. If the oil is dried at 100 C., it forms a solid which can beground and used as such. v

Example 4.Approximately 58 parts of hexamethylenetetramine ethylenedichloride reaction product (acid addition product) are treated withapproximately 33 parts of sodium mercaptobenzothiazole in aqueoussolution. The reaction product is a resinous product and may be purifiedalkyl, chlor, nitro substitution products of mercapto-aryl-thiazole, e.g., 5-nitro mercaptobenzothiazole, 5-chlor mercaptobenzothiazole, 3,5-dimethyl mercaptobenzothiazole, etc. The proportion of thiazole tofree base or acid addition product may be varied, as indicated by theabove examples,without departing from the invention.

Other salts of the mercapto-aryl-thiazole may be used such as those ofpotassium, ammonium, calcium, magnesium, zinc, etc., as well as thenitrogen base salts of the mercapto-aryl-thiazole, such as those ofethylamine, methylamine, etc.

Example 5.-In the following tests, the accelerator of Example 2, wascompounded in the proportion of 1 part and 1.25 parts, respectively, byweight based on the rubber, in a-rubber stock comprising by weight partssmoked sheet, 6 parts zinc oxide, blanc fix 40 parts, sulfur 2.25 parts,'acetone-diphenylamine (antioxidant) 3 parts. The cures are indicated inminutes and pounds /sq. inch steam pressure. T is tensiles/sq. in. and Eis percent elongation at break.

TABLE I Unaged stock Stock with Stock with 1 part 1.25 parts Cureaccelerator accelerator T V E '1 E After ageing 8 hours in an air bombStock with Stock with 1 part 1.25 parts Cure' accelerator accelerator "TE T E 3' eo#; 2230 920 2440 916 870 2370 783 740 2480 900 890 1830 850856 1930 880 I830 1750 900 Example 6.-In the following tests theaccelerator of Example 3 was compounded in the propor tion of 1 part byweight based on the rubber, in a rubber tread stock comprising by weight100 parts smoked sheet, 5 parts zinc oxide, carbon black 50 parts,stearic acid 2 parts, pine tar 1 part, sulfur 3 parts,acetone-diphenylamine 1 part. The cures were carried out at 274 F. forthe various intervals indicated in minutes.

The term rubber is employed in a generic sense to include caoutchouc,Whether natural or.

synthetic, balata, gutta percha, rubber isomers, and like productswhether fillers, pigments, antioxidants, etc.

The invention is to be understood as not limited to the exact procedurefollowed or proportions,

employed in the foregoing examples, which are illustrative only and notlimiting of my invention. Moreover, the invention is to be considered asnot limited by any theories advanced in explanation of the chemicalchanges involved in the manufacture of the compounds set forth but islimited'solely by the claims attached hereto. h

Having thus described my invention, what 1' claim and desire to protectby Letters Patent is: 1. A process of producing a vulcanized rubberproduct which comprises incorporating in rubber prior to actualvulcanization a mercaptobenzothiazole derivative of the free basereaction product of equi-mclecular proportions of formaldehyde and aprimary aliphatic amine salt of a non-oxidizing mineral acid.

2. A process of producing a vulcanized rubber product which comprisesincorporating in rubber prior to actual vulcanization a productresulting from reacting a salt of a mercaptobenzothiazole with areaction product of equi-molecular proportions of formaldehyde and anon-oxidizing mineral acid salt of an aliphatic amine.

3. A processof producing a vulcanized rubber product which comprisesincorporatingin rubber prior to actual vulcanization aproduct resultingfrom reacting an alkali salt of mercaptobenzothiazole with the reactionproduct of equi-molecular proportions of formaldehyde and ethylaminehydrochloride. 7

4. A process of producing a vulcanized rubber product which comprisesincorporating in rubber prior to actual vulcanization an arylene thiazylsulphide derivative of a reaction product resultor not admixed With ingfrom reacting equi-molecular proportions of formaldehyde and analiphatic amine salt of a non-oxidizing mineral acid.

5. A process of producing a vulcanized rubber product which comprisesincorporating in rubber prior to actual vulcanization an arylene thiazylsulphide derivative of a reaction product resulting from reacting equimolecular proportions of formaldehyde and an aliphatic amine salt ofhydrochloric acid.

6. A vulcanization accelerator composition comprising an arylene thiazylsulphide derivative of a reaction product resulting from reactingequimolecular proportions of formaldehyde with an aliphatic amine saltof a non-oxidizing mineral acid.

7. A vulcanization accelerator composition comprising an arylene thiazylsulphide derivative of the free base reaction product of equi-molecularproportions of formaldehyde and a primary aliphatic amine salt of anon-oxidizing mineral acid.

8. A vulcanization accelerator produced by reacting an arylene thiazylsulphide with a reaction product resulting from reacting equi-molecularproportions of formaldehyde and an aliphatic amine salt of hydrochloricacid.

WILLIAM E. MESSER.

